Field
The invention refers to a system and equipment to allow the transport and delivery of natural gas to a station or areas not supplied by gas pipelines. The invention combines a storage system and a hydraulic pressure system to allow transferring up to 95% of the stored gas from a storage cylinder to the customer with a pressure constant up to the end of the dispensing process.
Description of the Related Art
There are many known ways to transport natural gas. Due to its physical characteristics, natural gas does not liquefy even at high pressures. So, the natural gas transported at high pressure will be only at gaseous phase. Consequently, the relation of pressure parameters and the volume to be transported is very important for an economic gas transportation service. All materials of the construction must be specific for high pressure conditions and electrically classified areas.
Cryogenics is also used for gas transportation. In the case, the natural gas is liquefied at a very low temperature of about −161° C. and low pressure of less than 10 bar. The cryogenic transport is advantageous, as a cryogenic tank is capable to store a gas volume much higher in comparison to a high-pressure gas cylinder of equivalent volume capacity. However, the gas liquefying process presents technical problems. The natural gas liquefying process is very critical point. Although being a well known technology, it requires the use of specific materials, which has a higher cost due to the extremely low temperature condition of the process. This increases the process cost. Another disadvantage is that the cost for producing liquefied natural gas (LNG) is proportionally too expensive in view of the produced LNG, such that, as less is the production of a LNG facility as higher is the production cost (US$/m3 of produced LNG). This affects the application of the cryogenic technology for producing reduced amounts of LNG. Advantageously, our invention is economically feasible for producing reduced amounts, increasing its applicability.
Another technique involves the use of adsorbent material combined with pressure, wherein a pressure vessel or cylinder is filled with an adsorbent material. The authors Sidney Oliveira de Souza, Nelson Medeiros de Lima Filho and Cesar Augusto Moraes de Abreu—UFPE (Federal University of Pernambuco), in the article “Avaliação experimental do Processo de Carga para o Armazenamento de Gás Natural por Adsorção” states that the technology of Adsorbed Natural Gas (ANG) is being developed in the last decade, as a promising alternative for storing natural gas when compared to the CNG (compressed natural gas). The adsorption of natural gas on porous materials at relatively moderate pressures (60 to 80 bar) has many advantages in comparison to the CNG processes, as a large flexibility of design, construction and arrangement of a storage tank, increased safety and reduced costs. Although a promising technique, ANG is not commercially used, as it is still matter of research.
Finally, the most commonly storage of natural gas technique is the CNG, wherein the natural gas is compressed at high pressures and transported at gaseous phase to supply the customers. There are many possibilities for this service, as mentioned below.
The transport of compressed gas comprises cylinder pallets, wherein the compressed gas moves from pallet to pallet. They are individually filled in the compression station and the customer's pallets are changed as each pallet is consumed, as disclosed in Galileu's patents PI 0201043 and PI 0601501. However the solution proposed by Galileu is dangerous, as it is needed move pallets, which are too heavy.
The Gastron Comprimido S. A. patent PI 0604520 discloses a rigid structure for transporting cylinders storing fluids on the back of trucks attachable to a lifting system, which also describes the use of cylinder pallet.
The fractionated supply using cylinder pallets also has operational difficulties on the compression station. The use of such system reduces the amount of transported cylinders, decreasing the transported gas volume and increasing the cost per m3 of transported gas.
Neogás Inc has developed new technologies of gas compression and transferring for the transportation of gas, such that the cylinders used do not comprise any moving parts besides a special hydraulic fluid composition which avoids the mixing of oil and gas.
Igor Krasnov's patent application PI 0208143-1 (WO 02075204) refers to a compressed natural gas system, which consists of a control section, a transfer section, and a refueling section. The control section has a control panel and a hydraulic fluid reservoir, which contains the synthetic hydrocarbon hydraulic oil. The transfer section comprises banks of high pressure storage cylinders. Each bank has an equal number of cylinders, which are identical in size. The hydraulic fluid ports of each cylinder in the cylinder bank are coupled in parallel to a fluid manifold, wherein each fluid manifold has a manual shut-off valve. The cylinders have a first end and a second end, wherein the second end is closed. The first end having an opening through which passes a fitting, which contains a hydraulic fluid port and a gas port. A tracer element, as a disc, is positioned within the cylinder chamber, between the CNG and the hydraulic fluid. The tracer element has a high cost and a maintenance of difficult execution, as it is inside the cylinder.
Such an arrangement also has other disadvantages, which are described below. Besides the difficult maintenance of the disc, the use of the fitting may increase the chances of forming an emulsion, i.e., a friction between the oil and the gas. The use of the fitting also results in a reduced flow rate, increasing the time of dispensing or refueling the gas. When using a relief valve to maintain a pressure of 24.8 MPa, the compressing system requires the use of a specific type of cylinder, limiting the pressure and restricting the use of the system.
Patent document PI0006389-4 describes a cascade system for natural gas supply. The claimed system consists of a control section, a transfer section and a refueling section. The control section consists of a computerized control panel and a hydraulic fluid reservoir. The transfer section comprises two banks of high pressure storage cylinders. Each bank has an equal number of cylinders, which are identical in size. Each cylinder contains an axially moveable piston pair of inlets on one end and an outlet at the other end. The piston separates the compressed natural gas from the hydraulic fluid. The inlets of the cylinders in each bank are arranged in parallel to the inlet pipes.
In a compression system, it is possible to use a booster system for withdrawing gas from larger containers, in order to reduce costs. In this type of system there is high energy consumption. The booster works at low pressures around 220 bar. The system developed by Neogas maintains the initial pressure of the container without needing to elevate pressure, which also improves the time requested for refueling a customer. An advantage for the customer is that the refueling temperature of our system is lower than the booster system, as our system only need to maintain the gas compressed at the same temperature, which is different from the booster system that raises the pressure, raising the temperature. Thus, our system allows dispensing more gas than with the booster.
Patent P10603687-2 A of Neogás do Brasil describes a system of gas compression in a compression station, transportation, and gas delivery at constant pressure maintained by a special composition of a hydraulic fluid. The system described in that patent overcomes the deficiencies found in the prior art, disclosing a hydraulic pressure equipment able to refuel motor vehicle, maintaining pressure at a constant level, in a efficient manner. However, the system presents the drawback of comprising a complex driving system of valves of high cost.
Therefore, there is a need in the state of the art for a system and equipment of gas supply simpler and less expensive.
Thus, in order to overcome the problem of the state of the art mentioned above, the present invention discloses an improved control of the valve system by modifying the valve system and pipes. The invention improves driving the pneumatically actuated valves in a fastest and more synchronized manner. The use of extra-light cylinders type IV is optional. Optionally, a closed-cycle return block system of natural gas may be used.
Before detail the invention, it is important to show that the possibilities of use for the system of the invention. Both natural gas as a treated biogas can be used with this system. For a better understanding, find below the definition of both cases.
Natural gas is a fossil fuel formed when layers of animals and plants are submitted to intense heat and pressure over thousands of years, under the soil. The energy of the sunlight naturally absorbed by plants is stored in the form of carbon in natural gas. It is a mixture of light hydrocarbons found in the subsoil, in which methane has a higher content of over 70% by volume. The composition of natural gas can vary greatly depending on factors relating to the field in which the gas is produced, production process, conditioning, processing, and transport. Natural gas is a fossil fuel and a non-renewable source of energy.
Biogas is the name usually given to any gas produced from biologically break of organic matter in the absence of oxygen. Typically consists of a gas mixture consisting mainly of methane (CH4) and carbon dioxide (CO2), with small amounts of hydrogen sulfide (H2S) and humidity.
The biogas production occurs naturally in submerged locals where the atmospheric oxygen cannot penetrate, as in swamps, deep water bodies, intestine of animals, or in a anthropogenic condition, as in landfills and biogas plants.